The Ōuetsu Reppan Dōmei was a Japanese military-political coalition established and disestablished over the course of several months in early to mid-1868 during the Boshin War. Its flag was either a white interwoven five-pointed star on a black field, or a black interwoven five-pointed star on a white field. It is also known as the Northern Alliance .

Nihonmatsu Domain was a feudal domain under the Tokugawa shogunate of Edo period Japan, located in southern Mutsu Province. It was centered on Nihonmatsu Castle in what is now the city of Nihonmatsu, Fukushima, and its territory included all of Nihonmatsu, Motomiya, Ōtama and most of the present-day city of Kōriyama. For most of its history it was ruled by the Niwa clan. The Nihonmatsu Domain was also the scene of a major battle of the Boshin War of the Meiji Restoration.